With the rapid development of information technology and multi-service wireless network, there is an increasing demand for broadband wireless services. Frequency spectrum, as a precious non-renewable resource, is gradually becoming short. However, the conventional fixed frequency spectrum allocation strategy results in that a lot of frequency spectrum allocated to authorized users are not be used in certain time periods. Therefore, the spectrum utilization ratio is low, and a large amount of frequency spectrum is wasted. With the emergence of cognitive radio (CR) technology, the spectrum utilization ratio is improved, and the problem caused by insufficient spectrum resource is mitigated. Therefore, the cognitive radio technology becomes a research hotspot in the field of wireless communication.
A device (referred to as “a secondary device” herein) using the cognitive radio technology may opportunistically access to a legal frequency band of an authorized user equipment (referred to as “a primary device” herein) without affecting normal communication of the authorized user equipment. As such, dynamic spectrum access (DSA) is implemented, and the spectrum utilization ratio is improved.
The introduction of the cognitive radio technology can ameliorate the problem of insufficient spectrum resource. However, since different modulated signals are transmitted on the same frequency band, a primary device which operates on the same frequency band as a secondary device may be interfered by the signal transmitted from the secondary device. Therefore, an advanced algorithm is required to control the operating frequency and the transmission power of the secondary device, to ensure the communication quality of the primary device. In addition, the secondary devices operating on the same frequency band may interfere with each other. Thus the interference between the secondary devices should also be taken into consideration.
For a DSA system in which the secondary devices have different priorities (or QoS levels), it is required to design an interference suppressing method which may take the priorities of the secondary devices into consideration and guarantee different QoS for the secondary devices having different priorities, while the priorities of the secondary devices are not taken into consideration in currently existing interference suppressing methods.